§ Of the Rings of Power and the Third Age The Silmarillion

Even as the first shadows were felt in Mirkwood there appeared in the west of Middle-earth the Istari, whom Men called the Wizards. None knew at that time whence they were, save Círdan of the Havens, and only to Elrond and to Galadriel did he reveal that they came over the Sea. But afterwards it was said among the Elves that they were messengers sent by the Lords of the West to contest the power of Sauron, if he should arise again, and to move Elves and Men and all living things of good will to valiant deeds. In the likeness of Men they appeared, old but vigorous, and they changed little with the years, and aged but slowly, though great cares lay on them; great wisdom they had, and many powers of mind and hand. Long they journeyed far and wide among Elves and Men, and held converse also with beasts and with birds; and the peoples of Middle-earth gave to them many names, for their true names they did not reveal. Chief among them were those whom the Elves called Mithrandir and Curunír, but Men in the North named Gandalf and Saruman. Of these Curunír was the eldest and came first, and after him came Mithrandir and Radagast, and others of the Istari who went into the east of Middle-earth, and do not come into these tales. Radagast was the friend of all beasts and birds; but Curunír went most among Men, and he was subtle in speech and skilled in all the devices of smith-craft. Mithrandir was closest in counsel with Elrond and the Elves. He wandered far in the North and West and made never in any land any lasting abode; but Curunír journeyed into the East, and when he returned he dwelt at Orthanc in the Ring of Isengard, which the Númenóreans made in the days of their power.